1. Field of the Invention
The present invention relates to an image processing apparatus, and particularly relates to an image processing apparatus that can execute printing by using a special-color recording material, and preview image data which is output at the printing-execution time in advance.
2. Description of the Related Art
Usually, image processing apparatuses have been available as systems that capture drawing data transmitted from a host computer and that form image data based on the drawing data. The printing method used for the image processing apparatuses includes, for example, the electrophotography method. In a printing apparatus using the electrophotography method, a charger charges a photosensitive drum, and an electrostatic latent image is formed on the photosensitive drum with the write light corresponding to image data. A developer adheres toner to the electrostatic latent image so that the electrostatic latent image is developed to become a visible image. Next, the toner image is transferred from the photosensitive drum to a sheet, and fixed onto the sheet with heat or pressure.
In the image processing apparatus using the above-described electrophotography method, cyan, magenta, yellow, and black (CMYK) toner, where the term CMYK denotes basic printing colors which are referred to as process colors. Additionally, transparent toner is printed on part of or the entire printed image as a special-color recording material (see Japanese Patent Laid-Open No. 2006-251722, for example).
The special-color recording material includes toner other than the CMYK toner, such as green toner, orange toner, gold toner, silver toner, and the transparent toner.
Especially, the transparent toner is a transparent recording material provided to add a transparent image to a printed output. The use of the transparent toner allows for expressing a special texture including a glossy feeling, a luster feeling, a mat feeling, and so forth, which is different from that attained through printing performed only by using colored toner.
Further, systems providing the preview of printed output before performing printing by using the special-color recording material have been proposed (see Japanese Patent Laid-Open No. 2008-145784, for example). When printing and outputting print data by using the special-color recording material according to Japanese Patent Laid-Open No. 2008-145784, part of the print data, which is printed and output by using the special-color recording material, is detected in advance, and the detected part is displayed as a preview image by using a specified color or pattern.
Further, according to Japanese Patent Laid-Open No. 2008-145784, the off/auto/special-color settings can be made for displaying a preview image including the special-color recording material. For example, no preview image is displayed when the OFF setting is selected, and the color of part where the special-color material is adhered is detected and the preview image of a part having a color different from the detected color is displayed as a special-color part when the auto setting is selected. Further, when the special-color setting is selected, a position where the special-color recording material is adhered is displayed by using a color specified with a user.
When the effect of performing printing by using the special-color recording material is always constant (as is the case with solid shading performed by using a special-color orange or a special-color green, for example), a preview image provided to express the part where the special-color recording material is adhered may be generated according to the method disclosed in Japanese Patent Laid-Open No. 2008-145784. That is, a user can appropriately imagine the printing result based on specified colors or patterns that are displayed, as indicated by areas 101, 102, and 103 of FIG. 1. However, when performing printing by using transparent toner that has been available in the market in recent years, the reflectivity of light falling on the surface of a printed output can be changed. The above-described property of the transparent toner allows for applying a watermark pattern to the printed output and generating a decorative effect with texture. The transparent toner changes the light reflectivity based on the condition of an underlayer to which the transparent toner is applied. (Here, the term “underlayer” denotes the condition of the surface of a print medium (output sheet), which is attained before applying the transparent toner. An example of the property of the transparent toner, which changes the reflectivity based on the underlayer condition, will be described later.) When the transparent toner is applied to part of a sheet, a print effect achieved on the part through the use of the transparent toner is not always constant, which is different from the case where the solid shading is performed by using the special-color orange or the special-color green.
The light reflectivities that are changed based on the underlayer condition when printing is performed by using the transparent toner are illustrated in schematic diagrams 201, 202, 203, and 204 of FIG. 2 by the underlayer characteristics. The schematic diagram 201 illustrates the reflectivity of light falling on a printed output obtained by printing data on a sheet of paper having high smoothness, that is, coated paper by using the transparent toner.
No toner is used for a part (a) of the printed output at the printing time. Since the smoothness of the part (a) is still high, the reflectivity thereof is high. However, the transparent toner is used for a part (b) of the printed output at the printing time. The smoothness of the part (b) is lost due to asperities that are caused by the transparent toner, so that the light reflectivity is decreased.
On the other hand, the schematic diagram 202 of FIG. 2 illustrates the reflectivity of light falling on a printed output obtained by printing data on a sheet of paper having low smoothness, that is, mat paper by using the transparent toner.
Since the smoothness of the part (a) of the printed output, for which no toner is used at the printing time, is low, the reflectivity of the part (a) is also low. However, the printing is performed for the part (b) of the same printed output by using the transparent toner. Consequently, the asperities of the mat paper itself are smoothed so that the reflectivity is increased.
The schematic diagram 203 of FIG. 2 illustrates the case where data is printed on a print sheet by using toner including a coloring matter of which property is relatively similar to transparency, such as yellow toner. More specifically, the schematic diagram 203 illustrates the reflectivity of light falling on a part of the print sheet, where data is printed on the part by using the yellow toner, and other data is printed on the same part by using the transparent toner. The schematic diagram 203 illustrates the reflectivity of light falling on a part (a), which is attained when data is printed on the part (a) by using toner having the same property as that of the transparent toner, and other data is printed on the part (a) without using the transparent toner. The schematic diagram 203 illustrates the reflectivity of light falling on a part (b), which is attained when data is printed on the part (b) by using toner including a dye of which property is similar to that of the transparent toner, and other data is printed on the part (b) by using the transparent toner. The reflectivity of the part (a) is not significantly different from that of the part (b).
The toner including the dye of which property is similar to that of the transparent toner includes, for example, the yellow toner having a light-colored dye.
Usually, a comparison between a white color (a light-colored dye) and a black color (a dark-colored dye) shows that the light reflectivity of the black color is lower than that of the white color, because the black color absorbs more light than the white color. On the other hand, the light reflectivity of the white color is high, because the white color does not absorb light.
Since the yellow toner also has a light color, the light-absorption amount is little and the reflectivity is high, as is the case with the white color. Further, the transparent toner also has a light color and has the same property as that of the yellow toner.
Consequently, there is no difference between the light reflectivities that are obtained before and after the transparent toner having high reflectivity is adhered on the yellow toner having high reflectivity.
In relation to the schematic diagram 203 of FIG. 2, the schematic diagram 204 illustrates the light reflectivity attained in the case where data is printed on part of a print sheet by using toner including a dye of which property is different from that of the transparent toner, such as black toner, and other data is printed on the same part by using the transparent toner. The schematic diagram 204 illustrates the reflectivity of light falling on a part (a), which is attained when data is printed on the part (a) by using toner including a dye of which property is different from that of the transparent toner. The schematic diagram 204 also illustrates the reflectivity of light falling on a part (b), which is attained when data is printed on the part (b) by using toner including a dye of which property is different from that of the transparent toner, and other data is printed on the same part (b) by using the transparent toner. As is clear from the parts (a) and (b), the light reflectivities of the parts (a) and (b) are different from each other.
The reason why the above-described difference occurs is that the transparent toner having a high light reflectivity is adhered on the black toner that includes a dark-colored dye of which property is different from that of the transparent toner, that absorbs light, and that has a low light reflectivity, which is opposite to the case illustrated in the schematic diagram 203.
Thus, the properties of some of the special-color recording materials allow for changing effects that are produced on a finished printed output depending on the underlayer condition. When printing is performed by using the special-color recording material having the above-described property, it is difficult to make a user imagine the print result clearly by merely displaying a preview image produced before the printing is executed, where the preview image illustrates a part where the special-color recording material is printed by using a specified color.
Further, when the special-color recording material includes the same transparent coloring material as that of clear toner and a preview image is displayed, the preview image illustrating a part where the special-color recording material is applied only by using a substitute color that had already been set, an object including a coloring material other than the special-color recording material, the object being printed on the background, is hidden behind the substitute color image. Consequently, the print result which is significantly different from an output that shall be actually printed is presented as the preview image, which also makes it difficult for the user to imagine the print result.